Pretreatment and Fractionation of Wheat Straw Using Various Ionic Liquids

Pretreatment of lignocellulosic biomass with ionic liquids (as) is a promising and challenging process for an alternative method of biomass processing. The present work emphasizes the examination of wheat straw pretreatment using ILs, namely, 1-butyl-3-methylimidazolium hydrogensulfate ({[}bmim]{[}HSO4]), 1-butyl-3-methylimidazolium thiocyanate abmim]{[}SCN]), and 1-butyl-3-methylimidazolium dicyanamide ({[}bmim]{[}N(CN)(2)]). Only {[}bmim]{[}HSO4] was found to achieve a macroscopic complete dissolution of wheat straw during pretreatment. The fractionation process demonstrated to be dependent on the IL used. Using {[}bmim]{[}SCNI], a high-purity lignin-rich material was obtained. In contrast, {[}bmim]{[}N(CN)(2)] was a good solvent to produce high-purity carbohydrate-rich fractions. When {[}bmim]{[}HSO4] was used, a different behavior was observed, exhibiting similarities to an acid hydrolysis pretreatment, and no hemicellulose-rich material was recovered during fractionation. A capillary electrophoresis (CE) technique allowed for a better understanding of this phenomenon. Hydrolysis of carbohydrates was confirmed, although an extended degradation of monosaccharides to furfural and hydroxymethylfurfural (HMF) was observed.